The present automobiles have been required to reduce emission gas of specific substances such as carbon monoxide (CO), carbon hydride (HC) and oxide nitrogen (NOx) which are contained in emission gas from automobiles from a point of view of environmental preservation, and with the objective of these reduction, a direct injection engine (direct injection internal combustion engine) has been developed. In the direct injection internal combustion engine, fuel injection using a fuel injection valve is directly performed within a combustion chamber of a cylinder, and a particle size of fuel to be injected from the fuel injection valve is made small, whereby combustion of the injection fuel is promoted to reduce the specific substances in the emission gas and to improve output of the internal combustion engine among others.
In order to make the particle size of fuel to be injected from the fuel injection valve small, the need for means for pressurizing the fuel to high pressure arises, and for this reason, there have been proposed various techniques of a high-pressure fuel pump for pumping high-pressure fuel to the fuel injection valve (See, for example, Japanese Patent Laid-Open Nos. 10-153157, 2001-123913, 2000-8997, 11-336638, 11-324860, 11-324757, 2000-18130, and 2001-248515).
The technique described in the Japanese Patent Laid-Open No. 10-153157 improves fuel supply capacity in a high-pressure fuel supply device of the internal combustion engine, and in a variable discharge high-pressure pump of the device, to the pump chamber, there are communicated three passages, that is: a flow-in passage for flowing low-pressure fuel into the pump chamber; a supply passage for feeding high-pressure fuel to a common rail, and a spill passage. To the spill passage, there is connected a spill valve, and by an open-close operation of the spill valve, a spill amount to a fuel tank is controlled to thereby adjust the discharge. The technique of Japanese Patent Laid-Open No. 2001-123913 is to adjust the discharge by changing capacity of the pump chamber during a period from start of an intake stroke to immediately before end of a discharge stroke.
Also, the technique described in the Japanese Patent Laid-Open No. 2000-8997 controls a flow rate of high-pressure fuel to be supplied in response to injection quantity of the fuel injection valve, whereby even when a driving force of the high-pressure fuel pump lowers and a flow rate controlling valve does not operate, the technique supplies the fuel. When pressure on the downstream side (pressure chamber side) of the inlet valve is equal to or higher than pressure on the upstream side (inlet port side), a valve closing force occurs on the inlet valve, and there are provided an engaging member to which a biasing force has been given so as to engage when the inlet valve moves in a valve closing direction, and an actuator which exerts a biasing force in a direction opposite to the biasing force on the engaging member due to external input, and an open-close operation of the inlet valve adjusts the fuel discharge.
Further, the technique described in the Japanese Patent Laid-Open No. 11-336638 performs fuel metering accurately irrespective of the operating state of the internal combustion engine, and in a three-cylinder type pump, in order to prevent cycle variations in the fuel discharge, opening and closing of an electromagnetic valve is controlled in synchronization with feeding by the pump under pressure.
Further, also the technique described in the Japanese Patent Laid-Open No. 11-324860 enhances, in the variable discharge high-pressure pump, accuracy in flow rate control, miniaturizes the device, and reduces the cost. The technique described in the Japanese Patent Laid-Open No. 11-324757 improves, in a device for variable-controlling fuel injection pressure, response when target pressure changes, and the technique described in the Japanese Patent Laid-Open No. 2000-18130 relieves the fuel to be discharged from the fuel pump on the suction side through the use of an always-closed electromagnetic valve to control fuel pressure on the fuel injection valve side for improving the reliability.
Further, in the technique described in the Japanese Patent Laid-Open No. 2001-248515, a valve opening signal to be given to the always-closed electromagnetic valve is constructed so as to be completed at a predetermined position past a top dead center in the intake stroke from the top dead center of a fuel pump plunger toward a bottom dead center in order to prevent an abnormal rise in the coil temperature.
In a conventional operating timing chart for fuel pressure control by the variable discharge high-pressure pump, a REF signal 1801 is generated from a cam angle signal and a crank angle signal as shown in FIG. 27, and with the REF signal 1801 as a reference, a solenoid control signal (pulse) 1802 that is an actuator drive signal is outputted by angle or time control. Since a current flows through the coil for a while even if the solenoid control signal 1802 is terminated, the solenoid remains the attracting force as it is.
When, for example, the pump is required to discharge a small amount, the solenoid control signal 1802 is outputted (detail of control contents will be described later) in the vicinity of the plunger top dead center as shown in FIG. 27, and when the attraction force of the solenoid remains maintained up to the next discharge stroke at this time, the pump discharges the whole amount due to the characteristic of the high-pressure fuel pump. In other words, since the pump is required to discharge a small amount while the high-pressure pump discharges the whole amount, it becomes possible that measured fuel pressure follows the target fuel pressure.
Also, when the target fuel pressure 1803 calculated on the basis of the number of revolutions and load rises significantly as shown in FIG. 28, in order to cause measured fuel pressure 1804, that is actual fuel pressure, to follow the target fuel pressure 1803, as much fuel as possible is going to be discharged and F/B amount becomes larger, and therefore, the solenoid control signal 1802 is outputted in a domain, which is not an original domain to be discharged. If this output is continued, the solenoid control signal 1802 will be able to be outputted from the REF signal 1801, that is a reference point, as shown in FIG. 28.
In this case, for example, when the REF signal 1801 is not on a phase capable of pumping the fuel in the discharge passage, the high-pressure pump becomes unable to pump the fuel in the discharge passage, and on the other hand, the fuel injection valve injects the fuel, and therefore, the measured fuel pressure 1804 will become unable to follow the target fuel pressure 1803.
As understood from these examples, the conventional one will become unable to realize the optimum fuel pressure in an operating condition of the internal combustion engine, stable combustion will not be obtained because of fuel adherence to the surface of a piston or the like, resulting in a problem of worsened emission gas.
In other words, the present inventor has obtained knowledge that in control of the variable discharge high-pressure pump, timing of outputting the solenoid control signal, timing of terminating and control of its width are important. That is, the present inventor has obtained new knowledge that the high-pressure fuel pump control device calculates end timing of a drive signal of the actuator through the use of at least one of the number of revolutions of the engine, the injection quantity from the fuel injection valve, battery voltage, and coil resistance, limits to be prior to the top dead center of the plunger, and output timing of a drive signal of the actuator must be limited to be within a predetermined actuator operating time period that is a phase range capable of pumping, and within a time period until the plunger reaches the top dead center from the bottom dead center.
As regards each of the above-described conventional techniques, however, for example, transmitting open-close timing of a spill valve for adjusting an amount of fuel to be pumped to the common rail from the control device, and the like have been described, but concerning an item of restricting a control signal of the solenoid, which is an actuator of the variable discharge high-pressure pump, no description has been made, nor any special attention has been given to the above-described item.
The present invention has been achieved in view of such problems as described above, and is aimed to provide a control device of a high-pressure fuel pump of an internal combustion engine capable of improving stability in controlling the drive of the high-pressure fuel pump by limiting the end timing of a drive signal of the high-pressure fuel pump and driving an actuator in a control effective range of the high-pressure fuel pump.